Problem with virtio-scsi timeouts

[Douglas Miller <dougmill@xxxxxxxxxxxxxxxxxx>]

The problem I have seen is that the standard SCSI driver has a default 
timeout on I/O of 30 seconds. But when this driver is used on a KVM 
guest via virtio-scsi, the host should be controlling the timeout based 
on the actual type of media, and those timeouts may need to be longer. 
The KVM guest 'sd' I/O then happily timeout at 30 seconds and try to 
abort the commands. With a heavy I/O load it become likely that an abort 
will also timeout and this leads to fatal errors like filesystems going 
offline.

It seems that the virtio-scsi driver should disable the 'sd' timeout and 
allow the host to handle that. Maybe this has been done already and just 
not been backported to distros, but is it reasonable to disable the 'sd' 
timeout in KVM guests? Or at least should the default timeout be 
increased to a much larger value?

Thanks,

Doug